Arthritis is a costly disease to society and the individual. The annual costs in the US due to arthritis exceed $86 billion. Nearly 8 million Americans are disabled as a result of their arthritis, making arthritis a primary cause of disability in the US. Knee osteoarthritis (OA) and rheumatoid arthritis (RA) are major causes of arthritis-related disability. Physical activity is a promising weapon in the public health arsenal to improve the health of persons with arthritis. Our recent work indicates that increased levels of physical activity reduced disability progression in an observational cohort of adults with arthritis. Since medical costs due to arthritis are strongly driven by disability, identifying an implementable physical activity intervention that reduces disability among persons with arthritis may provide an effective strategy to contain rising health care costs due to arthritis To examine disability progression and economic issues relevant to the promotion of physical activity in rheumatic disease, an ancillary study to the Physical Activity Management (PAM) Trial is proposed. The PAM Trial is an NIH-funded randomized clinical trial enrolling 480 patients with knee OA and RA. The funded mission of the PAM Trial is to test the effectiveness in terms of health status of a physical activity management program to augment physician physical activity promotion (PAM group) compared to only physician promotion of physical activity (control group). This ancillary study extends this randomized clinical trial beyond clinical outcomes to factors relevant to pubic policy evaluations of this intervention. The proposed ancillary study requests funds to add 1) disability measures, 2) a community-based health utility assessment of health related quality of life, and 3) medical utilization measures to the funded PAM Trial. These new measures will extend the evaluation of PAM physical activity management beyond its effect on pain and health status to an assessment of policy-relevant outcomes. Specifically, this randomized clinical trial will be used to determine if PAM is a cost-effective intervention that reduces disability progression and improves health related quality of life of patients with arthritis. This is key information for policy evaluations related to the potential large scale dissemination of the PAM intervention into widespread practice. Findings from this study will advance public health and policy efforts to reduce disability, rising health care costs, and improve the quality of life among 48 million US adults having arthritis.